With some advantages such as high quality, small size, light weight and a wide range of applications, liquid crystal display (LCD) screens have been widely used in smart phones, notebook computers, desktop monitors, televisions and other types of consumer electronics products, and have gradually replaced the traditional cathode ray tube (CRT) display screen and became one of the mainstreams in display field.
At present, high quality and high resolution is the main developing goal of LCD screen, and the frame rate is upgraded from the original 60 Hz to 240 Hz. However, the conventional liquid crystal has a limited response speed due to the material properties. In contrast, the blue phase liquid crystal (BP-LC) has some advantages such as higher response speed and no need of alignment film; for example, the response time may down to sub-milliseconds (<1 ms). Therefore, BP-LC is regarded as the future of the liquid crystal material.
Conventionally, blue phase liquid crystal exists in a quite narrow temperature range, which is about only 1˜2° C. In order to enlarge the temperature range, Professor Kikuchi at Kyushu University in Japan disclosed polymer-stabilized blue phase liquid crystal (PSBP-LC) in 2002. Specifically, through doping a small amount of polymer of monomer in the blue phase liquid crystal and performing UV light irradiation, monomer is bonded into polymer according to photo polymerization and the temperature range of the BP-LC can be raised up above 60° C.
The working principle of blue phase liquid crystal is based on the Kerr effect, which indicates that the refractive index of materials will vary with the applied voltage and has a relationship Δn=λKE2, wherein λ is the wavelength of the incident light, K is the Kerr constant, E is the electric field strength. The aforementioned polymer-stabilized blue phase liquid crystal method can successfully enlarge the temperature range of blue phase liquid crystal; however, a decreasing K is accompanied, which may result in an increasing required driving voltage.
To overcome the problem of insufficient driving voltage, one method is to employ a LCD booster circuit for raising the required driving voltage. However, because having a relatively-complicated circuit structure and a relatively-large element number, the conventional LCD booster circuit has a relatively high overall manufacturing cost. Another way to overcome the problem of insufficient driving voltage is through employing a novel manufacturing structure. For example, as illustrated in FIG. 1, a passivation 9 is formed between the substrate and the transparent conductive film (ITO) 8. Through this specific manufacturing structure, enhanced electric field efficiency is obtained at the liquid crystal driving electrode. However, the required driving voltage is still up to 30˜40V even the aforementioned structure is employed; thus, it is quite difficult to apply the structure to some specific applications and in commercialization.
Therefore, it is quite necessary to design a circuit and a method capable of effectively increasing the driving voltage of the booster circuit, so that the blue phase liquid crystal is not only able to receive a sufficient driving voltage but also having a simplified circuit structure, reduced number of circuit elements and reduced cost.